Thermometer probe

ABSTRACT

Extending from a handle grip is an elongated hollow metal tube with an outer open end. The interior cavity of the tube contains a quantity of foamed plastic, the outer end of which is generally conically shaped and extends beyond the open tube end. A thermistor is located at the tip of the foamed plastic cone and a thin coating of rigid cementitious material is provided over the exposed end of the plastic, metal tube and side portions of the thermistor to secure the thermistor into a fixed position. A removable plastic envelope or sheath is received over the tube and exposed thermistor, with the thermistor bottoming against the inner tube end wall.

United States Patent Mead et a1.

[ THERMOMETER PROBE [72] Inventors: Carver A. Mead, 2036 Pasadena GelnRoad, Pasadena, Calif. 91107; Stephen Kurtin, 536 S. Euclid Ave.,Pasadena, Ca1if.91l06 [.22] Filed: July 1, 1970 [21] App1.No.: 59,790

A AQ/i 72/5 1 1 July25, 1972 Ensign et a1. ..73/362 AR Glick ..73/362 ARPrimary ExaminerLouis R, Prince Assistant ExaminerFrederick Shoon [57]ABSTRACT Extending from a handle grip is an elongated hollow metal tubewith an outer open end. The interior cavity of the tube contains aquantity of foamed plastic, the outer end of which is generallyconically shaped and extends beyond the open tube end. A thermistor islocated at the tip of the foamed plastic cone and a thin coating ofrigid cementitious material is provided over the exposed end of theplastic, metal tube and side portions of the thermistor to secure thethermistor into a fixed position. A removable plastic envelope or sheathis received over the tube and exposed thermistor, with the thermistorbottoming against the inner tube end wall.

. of temperature,

THERMOMETER PROBE The present invention relates generally to themeasurement and, more particularly, to an improved temperature measuringprobe including a thermistor as an active element for taking bodytemperature for clinical purposes.

BACKGROUND OF THE INVENTION In the past, the standard means for takinghuman body temperature has been through the use of a conventionalmercury thermometer. As is well known, these thermometers not onlyrequire a relatively long period of time to register a new temperature,but also they must be shaken after each reading to reset the mercuryinto the bulb. Both of these requirements are manifestlydisadvantageous, especially where a number of patients must have theirtemperatures taken periodically.

There are known faster acting electrical thermometer systems which relyupon a thermistor as the primary temperature sensing element. Athermistor is a component the electrical resistance of which varies in aknown manner as a function of temperature. Typically in such systems,the thermistor has been incorporated into an electrical circuit forgenerating an output indication following the thermistor resistance, andthus can be calibrated to give a direct output reading of temperature.

Known thermistor probes for use in electrical temperature measuringsystems are not completely satisfactory, for one reason or another. Incertain known devices, the thermistor has been left exposed to directcontact with body surfaces, giving rise to a continuing problem ofpossible damage to the thermistor during, use or cleaning after use,necessitating its replacement. In other cases, the thermistor is soconstructed as to be maintained in contact with a mass of materialduring use whereby the reaction time of the probe is substantiallylengthened.

SUMMARY OF THE INVENTION In accordance with the practice of the presentinvention, there is provided an improved thermometer probe for hand helduse. Extending from a handle grip is an elongated hollow metal tube withan outer open end. The interior cavity of the tube contains a quantityof foamed plastic, the outer conical end of which extends beyond theopen tube end. A thermistor is located at the tip of the foamed plasticcone, with connecting wires thereto extending axially through theplastic body into the handle portion for connection to externalelectrical apparatus via a cable. A thin coating of rigid cementitiousmaterial is provided over the exposed end of the plastic, metal tube andside portions of the thermistor to secure the thermistor. A removableplastic envelope or sheath is received over the tube and exposedthermistor, with the thermistor bottoming against the inner tube endwall. In use, that part of the probe including the plastic covering isinserted into the appropriate body cavity in which temperature is to betaken and the thermistor is accordingly varied in resistance responsiveto the temperature of the environment, which change in temperature isreflected through associated electrical apparatus to provide a directindication of the body temperature.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of thetemperature measuring apparatus of the present invention.

FIG. 2 is a sectional, partially fragmentary, enlarged view of thetemperature probe of the present invention taken along the line 2-2 ofFIG. 1.

FIG. 3 is a perspective view of the probe end of the present inventionshowing a removable covering in phantom.

DESCRIPTION OF A PREFERRED EMBODIMENT With reference now particularly toFIG. 1 of the drawings, the temperature measuring probe of the presentinvention is seen to comprise in its major elements a cylindrical handle11, a flange 12 forwardly of the handle, and an elongated shaft portion13, the latter including the temperature sensor means of a specialconstruction to be described later herein. In use the handle 11 is heldin the fingers of the nurse or attendant and the shaft portion 13 isinserted into the appropriate body cavity. The body temperature of thepatient immediately surrounding the sensor enclosed within the shaft 13produces an electrical signal change via the cabling l4 and digitalreadout circuit 15 which provides direct temperature display as at 16,for example.

With reference now particularly to FIG. 2, the shaft portion 13 is seento include a hollow metal cylindrical tube 17, which has the outer endportion of its central cavity filled with a body of foamed plastic 18which extends outwardly of the tube end to terminate in a cone 19. Atthe cone apex, there is located a temperature responsive element 20having the property of changing its electrical characteristics as afunction of temperature. Although other temperature responsive materialsmay be found useful in this regard, best operation has been obtained todate with an element known as a thermistor which provides a generallyexponential change of electrical resistance as a function of ambienttemperature. The other end of the tube 17 is afiixed to the handleportion in a suitable manner (not shown).

Attached to the thermistor 20 are a pair of fine wire leads 21 which, inturn, are connected to larger leads 22. The leads 21 and 22 may beaxially threaded through the foamed plastic body 18, or a passageway maybe first formed in the body by a needlelike tool, for example, afterwhich the wires may be inserted in the passageway. The fine wire leads21 are approximately 0.002 inches in diameter and constructed of a metalhaving relatively low heat conductivity such as constantan, Nichrome orstainless steel, for example, which will not draw a significant amountof heat from the thermistor and thereby leaves the thermistor moreclosely reflecting the true ambient temperature. The leads 22 areconnected within the handle 11 to the cable 14 in a conventional manner.

A cementitious material 23 which is rigid on setting up, is applied in athin coating over the outer surface of the cone l9 and onto the endedges of the tube 17, as well as extending along the inner surface ofthe tube for a limited distance. The material 23 also engages the sideportions of the temperature responsive element 20 while leaving itsoutwardly directed surface exposed. In this way, the element 20 isintegrally secured with the metal tube 17 and the foamed plastic 18 by ameans which provides a poor conductive path for heat as well as a lowheat mass for absorption of heat. That is, although the sensing element20 is precisely positioned at the cone apex and firmly anchored againstdislodgement, it is contacted by securing means constructed ofrelatively low heat conducting materials.

A disposable thin wall plastic sheath 24 is removably received over thetube 17 with its side walls spaced from the tube as at 25 and the closedend wall brought into bearing contact with the element 20 when fullyseated. It is important that this sheath have a sufiiciently thin wallsuch that the element 20 will quickly respond to the ambienttemperature. That is, the sheath has the dual functions of protectingthe element 20 and adjoining surfaces of the probe and also providing arapid conduction of heat therethrough. The sheath or envelope 24 iscontemplated for but a single use, after which it is removed, thrownaway and a new one placed thereon for use with another patient.

In an actual construction of the invention, the foamed plastic body 18was constructed of a urethane plastic included within a thin wallstainless steel tube 17; and the cementitious material 22 consisted ofan epoxy, using a No. 4206 base with a 3490 hardener, both manufacturedand sold by the Hysol Company. The probe cover or sheath was made ofpolyethylene having a body wall thickness of 0.007-0.0l0 inches.

There is provided in accordance with the practice of the presentinvention a thermistor probe for use in taking body cylinder end into anintegral unit by enclosing all but the thermistor tip in a rigid coatingprovides an exceptionally rugged construction capable of withstandingrepeated emplacement and removal of probe covers without adverse effect.In actual use, the probe covers are pushed in place and pulled orsnapped off in such manner as to subject the probe tip to significantforces which, lacking the firm and durable thermistor mountingarrangement of this invention, could quickly destroy or impair probeoperation.

temperature which is exceptionally fast acting. The thermistor mountingis isolated from all probe parts having high heat capacity whereby thethermistor can quickly reflect temperature change without the adversereaction time effect of a proximate high heat capacity body. Moreover,since the thermistor 5 and immediately adjacent portions of thecontacting probe cover form a low heat mass, the probe may beadvantageously used to take temperature measurements at parts of thebody having low heat mass. For example, in taking the temperature at theback of the throat with a high heat capacity probe, the probe canwithdraw sufficient heat from the low heat mass tissues to introduce aserious error in the throat surface temperature measurement.

Forming the thermistor, protruding foam plastic and metal What isclaimed is:

trical processing and display apparatus, comprising:

handle means;

a hollow metal tube having one end afiixed to the handle means;

a foam plastic plug received within the other end of the tube 'andhaving generally conical portions protruding from said tube end;

a thermistor mounted to the outer end surface of the plug;

a thin coating of a rigid, low heat conducting material adhered to thetube, protruding plug portions and parts of the thermistor; and

a removable thin wall plastic cover received over said thermistor, plugand tube, said cover being maintained spaced'from said tube throughoutand having a closed end which is in bearing contact with the thermistor.40 2. A clinical body temperature sensing probe for use with electricalmeasuring apparatus, comprising, in combination:

handle means; a hollow open-ended tube having one end affixed to thehandle means;

a body of low heat capacity material included within the other end ofthe tube and extending outwardly therefrom;

heat responsive means mounted onto an outwardly directed surface of saidlow heat capacity body, said heat responsive means exhibiting anelectrical characteristic of value functionally related to itstemperature;

means interconnecting the heat responsive means and the electricalmeasuring apparatus;

a thin film of rigid low heat capacity material unitarily joining thetube, body of low heat capacity material and the heat responsive means;and

a low heat capacity, hollow tube shield having an open end and a closedend, said open end being received over the end of the tube and removablyretained on said handle means, and said closed end being in contactingrelation with the heat responsive means.

3. A clinical temperature probe as in claim 2, in which the heatresponsive means includes a thermistor mounted on an outwardly directedsurface of the body of low heat capacity material and having an exposedsurface free of the coating.

4. A clinical temperature probe as in claim 2, in which the body of lowheat capacity material includes a foamed plastic plug fittingly receivedwithin the end of the hollow tube.

5. A clinical temperature sensing probe for connection with electricalmeasuring apparatus, comprising:

, a handle;

a hollow, open-ended metal tube having one end secured to the handle andextending outwardly therefrom; a plastic foam plug received within theother end of the tube and having a tapered portion extending outwardlyof the tube;

a thermistor mounted onto the outer end surface of the plug taperedportion;

a thin film of epoxy over the plug tapered portion, tube end and partsof the thermistor integrally securing the same; lead wire meansconnected to the thermistor and extending through the plug, tube andhandle for interconnection with the measuring apparatus; and anelongated, thin-wall tubular plastic shield having an open endfrictionally retained to handle, the side walls of which shield aremaintained spaced from the tube, and a closed end wall which contactsthe thermistor.

1. A clinical thermometer probe for use with external electricalprocessing and display apparatus, comprising: handle means; a hollowmetal tube having one end affixed to the handle means; a foam plasticplug received within the other end of the tube and having generallyconical portions protruding from said tube end; a thermistor mounted tothe outer end surface of the plug; a thin coating of a rigid, low heatconducting material adhered to the tube, protruding plug portions andparts of the thermistor; and a removable thin wall plastic coverreceived over said thermistor, plug and tube, said cover beingmaintained spaced from said tube throughout and having a closed endwhich is in bearing contact with the thermistor.
 2. A clinical bodytemperature sensing probe for use with electrical measuring apparatus,comprising, in combination: handle means; a hollow open-ended tubehaving one end affixed to the handle means; a body of low heat capacitymaterial included within the other end of the tube and extendingoutwardly therefrom; heat responsive means mounted onto an outwardlydirected surface of said low heat capacity body, said heat responsivemeans exhibiting an electrical characteristic of value funCtionallyrelated to its temperature; means interconnecting the heat responsivemeans and the electrical measuring apparatus; a thin film of rigid lowheat capacity material unitarily joining the tube, body of low heatcapacity material and the heat responsive means; and a low heatcapacity, hollow tube shield having an open end and a closed end, saidopen end being received over the end of the tube and removably retainedon said handle means, and said closed end being in contacting relationwith the heat responsive means.
 3. A clinical temperature probe as inclaim 2, in which the heat responsive means includes a thermistormounted on an outwardly directed surface of the body of low heatcapacity material and having an exposed surface free of the coating. 4.A clinical temperature probe as in claim 2, in which the body of lowheat capacity material includes a foamed plastic plug fittingly receivedwithin the end of the hollow tube.
 5. A clinical temperature sensingprobe for connection with electrical measuring apparatus, comprising: ahandle; a hollow, open-ended metal tube having one end secured to thehandle and extending outwardly therefrom; a plastic foam plug receivedwithin the other end of the tube and having a tapered portion extendingoutwardly of the tube; a thermistor mounted onto the outer end surfaceof the plug tapered portion; a thin film of epoxy over the plug taperedportion, tube end and parts of the thermistor integrally securing thesame; lead wire means connected to the thermistor and extending throughthe plug, tube and handle for interconnection with the measuringapparatus; and an elongated, thin-wall tubular plastic shield having anopen end frictionally retained to handle, the side walls of which shieldare maintained spaced from the tube, and a closed end wall whichcontacts the thermistor.